DESCRIPTION: (From applicant's abstract) The primary object of the Colorado Adoption Project is to assess genetic and environmental influences on individual differences in behavioral development among children. The study includes biological parents who relinquished their children for adoption at birth, adoptive parents, matched "control" (nonadoptive) parents, and the children (probands and siblings) in these families. Adults were administered a three-hour battery of behavioral tests that included measures of cognitive abilities and personality, information pertaining to family background, common medial and behavioral problems, interests and talents, and frequently used drugs. For the children, the assessments employ standard tests of cognitive and language development, personality/temperament, motor development, and health. Environmental assessments in the adoptive and control homes are emphasized. The adopted and control probands and their younger siblings are studied in their homes at 1, 2, 3, and 4; in the laboratory at 7, 12, and 16 (at 16 they are administered the same test battery completed by their parents over a decade-and-a-half earlier); and by telephone interviews at 9, 10, 11, 13, 14 and 15. The proposed study will complete the assessment of adopted and nonadopted probands, as well as most of their siblings, through late adolescence (i.e., through age 16). In addition, the project will include a sample of nearly 340 twin pairs who have been previously tested through age 12, using many of the same measure as the CAP sample. By incorporating the power of the twin design into the parent-offspring and sibling analyses of the CAP, both statistical power and the range of testable hypotheses regarding genetic and environmental influences are increased, resulting in a landmark adoption, sibling, and twin study of child development. By YEAR 26, the numbers of adopted and non-adopted children who will have been tested at 13,14,15 and 16 years of age, respectively, are 614, 612, 538, and 663. In addition, 349, 266, 174, and 212 twin pairs will be tested at 13,14,15 and 16 years of age, respectively. The proposed continuation of HD-10333 provides an important opportunity to reap the harvest from the 21 years of previous support for this landmark study, advancing basic research in child development, with important implications for education, mental health, and child rearing practices. A genetically informative study of behavioral development of this magnitude and quality has never before been undertaken, and it is unlikely that such and opportunity will occur again.